Download Infectious Bronchitis in Parent Stock

Infectious Bronchitis in Parent Stock
February 2009
By Rik van den Bos, Company Veterinarian, Aviagen
SUMMARY
Who Should Read This Article
This article is mainly targeted at veterinarians and production managers.
What is this Article About
IBV is increasingly being seen as a cause of poor peak
production, egg quality and hatchability. It has a significant impact on the economic performance of a flock.
Providing adequate protection against IBV is therefore a
vital part of parent stock management. This article provides information on the key aspects involved in providing protection against infection from IBV.
Symptoms of IBV
Physical bird symptoms include respiratory gasping,
coughing, sneezing, tracheal rales and nasal discharge.
Generally, birds appear depressed and have reduced feed
intake.
In adult breeders the clinical signs are often accompanied by a loss in production after peak. This loss can be
as much as 40% but it is generally between 10 and 15%.
Increasingly no peak in production is seen, rather a flat
plateau in production.
Birds infected in the rearing period can look physically
well but can have an incomplete or absent oviduct.
Mortality varies and is mainly caused by secondary bacterial infections.
Eggs can be smaller and paler in color and may be soft
shelled or misshapen with increased calcareous deposits.
Internal albumin quality is poor.
Risks of Infection
• IBV is highly infectious.
• Transmission is via direct and indirect contact between poultry and poultry premises (people, vehicles, etc.).
• The risk of IBV is increased in farms not cleaned
out properly or disinfected or where built-up litter
is used.
• Multi-age sites pose a high risk of transmission
and infection with IBV.
Protection
A high biosecurity standard, with the controlled
movement of equipment and personnel as well as
proper cleaning and disinfection of housing is necessary to protect against IBV.
An adequate vaccination program and the appropriate
administration of the vaccine are also essential. Establishing the correct vaccination program is difficult
and serology is important to identify the presence of
any variants. In order for vaccination to be effective
it is important that:
• Vaccine storage and transport are correct.
• Vaccine application is correct and that a uniform
uptake is achieved.
• Vaccine response is monitored.
Treatment
There is no treatment for IBV, but treatment with antibiotics to prevent secondary bacterial infections is appropriate.
TAKE HOME POINT
A high biosecurity standard is required with correctly delivered early vaccination between the first and second week of the bird’s life. These are critical for helping prevent any future production issues.
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The remainder of this article provides more detail on the points summarized on page one.
Introduction
Infectious bronchitis virus (IBV) is an acute, highly contagious disease which can have a significant effect on egg
production and egg quality. Increasingly IBV is being
seen in the field as a cause of poor peak production, egg
quality and hatchability. The occurrence of IBV can have
a considerable impact on the economic performance of a
flock. It is therefore important that procedures are put in
place to ensure flocks are adequately protected against
infection from the IB virus.
This article provides information on how to recognize if
the disease is present in a flock and the procedures that
need to be put in place to provide adequate protection
against the occurrence of IBV.
Background
Infectious bronchitis was first diagnosed in the United
States in 1930 and now occurs worldwide. Numerous
different serotypes have been identified since the originally identified Massachusetts type in 1950.
IBV is a highly contagious respiratory disease characterized by upper respiratory signs, such as tracheal rales,
coughing and sneezing. It can be part of a mixed infection
causing airsacculitis and may affect egg production and
egg quality.
Transmission
The IB virus is not vertically transmitted, but transmission via surface contamination of the egg with feces
is possible. Infectious bronchitis can replicate in tissues
of the respiratory tract, intestinal tract, kidneys and
oviduct. The virus is periodically shed in nasal excretions and feces for up to 20 weeks after clinical recovery
from the infection. Once exposed to poultry the virus
spreads rapidly in a flock. The incubation period is 18-36
hours, depending on the infectious dose and the route of
infection. All birds in a flock will become infected, but
mortality is dependant on:
• the serotype of the virus.
• age of the birds.
• immune status (maternal, active or influence of
immunosuppressive diseases).
• environmental stress e.g. ammonia levels.
• other respiratory viruses and bacterial infections.
The highly infectious nature of the virus combined with
the long shedding period and the possibility of carrier
birds means a high biosecurity standard is essential if
infection with IBV is to be avoided. The risk of flock to
flock transmission via contamination of personnel and/
or equipment is high. To prevent this strict control of the
movement of people, vehicles and equipment is required
between poultry sites. Proper biosecurity and hygiene
control on a multi-age site is very difficult.
Most serotypes of IBV are inactivated after 90 minutes at
45ºC. During the colder winter months survival can be
up to 50-60 days, and in fecal material it can stay alive
for up to 100 days. The virus is sensitive to commonly
used disinfectants, but for disinfectants to be effective
all organic material, especially feces, should be removed
from the houses during clean out. Disinfectants should
be used at the suppliers recommended dose rate.
Clinical Signs
Respiratory signs, like gasping, coughing, sneezing,
tracheal rales and nasal discharge are commonly found.
Wet eyes with swollen sinuses may also be seen. Birds
appear depressed, and feed consumption is reduced.
Mortality is mainly caused by secondary bacterial infections. Duration of the disease could be up to 10 days, but
may last longer if a severe bacterial infection is present.
Breeders infected during the rearing period with a serotype
affecting the kidneys may recover from the respiratory
symptoms but tend to develop ruffled dirty feathers with
frequent flushing and consequential wet litter due to the
increased water intake.
In adult breeders the clinical respiratory signs are often
accompanied by a decline in egg production.
Commonly there are two scenarios seen:
1. The classical egg production curve with a drop in egg
production after peak. This decline may be as much
as 40%, but in general a drop of 10-15% is seen.
2. No clearly defined peak in egg production is seen;
rather a flat plateau in production occurs after 40-60%
production. This type of decline in egg production is
increasingly being seen in the field (Figure 1).
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Hen Housed %
Figure 1: Example of egg production curve in a flock
infected with IBV showing no peak and a plateau in
production after 60%.
Hen housed egg production
90
80
70
60
50
40
30
20
10
0
Standard HH
Actual HH
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25
27
29
31
33
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False Layers
Recently in Europe, Asia and the Middle East there have
been concerns over the early infection of young female
parent stock with infectious bronchitis, causing permanent
destruction of the oviduct. Birds that were otherwise
healthy with good body weights and CV’s did not reach
peak production. Post mortem examination revealed an
incomplete or absent oviduct or the presence of a thin
walled cystic oviduct (Figure 3). Birds showing these
symptoms are commonly referred to as ‘false layers’, as
they visit the nests on a regular basis and cannot be differentiated from normal layers from their physical appearance.
Figure 3: A thin walled cystic oviduct
Flock age - weeks
Generally egg production will slowly increase within
eight weeks, but normal production is rarely achieved.
Together with these production problems, a change
in external and internal egg quality is also frequently
observed. When a flock is infected with IBV eggs are
typically smaller in size and pale to the point of some
being completely white. Eggs may also be soft shelled,
misshapen or have calcareous deposits (Figure 2).
Figure 2: Examples of egg defects caused by IBV
infection
In a large number of these ‘false layers’ a new variant of
IBV was detected; early infection with this variant has
been seen to result in a failure of the oviduct to develop,
despite the other characteristics of sexual maturity
occurring normally (Figure 4). The GD – Animal Health
Service in Deventer, Netherlands, has typed this IBV
variant as D388. This strain has been confirmed as being
identical to the QX-like variant, which was typed and
described in China in 2004.
Figure 4: Examples of no oviduct development as a result
of early infection with IBV
The egg on the left has calcareous deposits and the egg
on the right has a soft shell.
Internally the albumin of the egg may become thin and
watery with no clear distinction between the thick and
thin albumin.
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Protection
A high biosecurity standard which controls the movement
of personnel and equipment, and preferably an all-in
all-out system with proper cleaning and disinfection of
the houses is necessary if protection against IBV is to be
maximized. Vaccination offers further protection against
the disease. Vaccines for IBV can be both live and inactivated. Live vaccines replicate in the respiratory tract
stimulating local and systemic immunity. Inactivated
vaccines help to stimulate uniform and persistent titers.
Inactivated IBV vaccines do not stimulate local, cellmediated immunity as effectively as vaccines containing
live virus. Inactivated or killed vaccines are administered
by injection of individual birds and are used in breeders
around 18 weeks of age. For an inactivated vaccine to be
effective, the birds need to be primed with a live vaccine
at least five weeks before administration of the inactivated
vaccine.
In order for vaccination against IBV to be effective the
following are important:
• Appropriate storage and transport of vaccine. Monitor
the storage conditions, keep the vaccine refrigerated,
prevent direct sunlight and administer before expiratory date.
• Application and uniform intake. Use proper and clean
equipment for spray vaccination. Use clean water and
cleaned waterlines before water vaccination; always
adhere to the recommendations of the pharmaceutical
company.
Non-specific and Specific Immunity
For protection against an IBV challenge both non-specific
and specific immunity is required.
The non-specific immune system includes body temperature, micro-flora of the intestine and cilia (hairs) and
mucus in the respiratory tract. Mucus secretions trap the
virus particles, which are then transported out of the body
via cilia. The effectiveness of the non-specific immune
system will be reduced if other factors such as brooding,
ventilation and nutrition are not optimal; minimizing
stress and practicing proper brooding management are
very important. Poor nutrition leads to deficiencies in nonspecific and specific immune systems; viruses (and other
organisms) are able to penetrate the protective coverings
like the intestine and at the same time the development of
immunity is reduced, so the antibody response is insufficient. It is therefore important that feed of good physical
quality, containing good quality proteins and vitamins, is
provided.
Specific immunity is both passive and active. Passive
immunity consists of maternally derived antibodies
which will give the chick systemic protection for a limited
period of time, and will reduce the vaccine reaction after
vaccination with a live virus. Maximum concentrations of
circulating maternal antibody occur in the young chicks at
one to three days of age, as the yolk sac is absorbed, and
is usually depleted at 18-24 days of age.
Because maternally derived antibodies only give a
systemic protection for a short time, it is recommended
to give a live vaccination in the hatchery or as soon as the
birds arrive on farm via coarse spray or eye drop. This
will establish local protection by blocking receptor cells
in the upper respiratory tract, produce antibodies locally
and will be the first defense against an early challenge.
Vaccination Programs
With all the different IBV strains that exist around the
world, establishing the correct vaccination program is
difficult, however antibodies produced to one variant
often show (part) cross protection to other variants. Where
prevalent strains in an area have been identified, designing
a vaccine program using commercially available vaccine
is often possible.
No combination of IBV vaccine strains provides full
protection against all the different IB challenges, although
there are combinations which broaden the coverage. The
vaccine program should include the use of two different
IBV vaccines. In general it’s not recommended to
vaccinate with multiple live IBV serotypes at one time,
as this can lead to the development of poor immunity and
excessive vaccine reaction, but depending on the challenge
it is sometimes necessary. For example a classical strain,
like H120 or a Massachutes-strain at day 0 may be used
in combination with a variant strain, like 4/91 or 793B at
10-14 days of age.
The combination of a classical with a variant strain will
increase protection against a broader range of serotypes
and will give better protection against QX/388 strain. This
will help prevent ‘false layers’, where early protection
is very important. Recent research has also shown that
protection against ‘false layers’ was achieved when the
Arkansas strain was used in combination with a classical
strain.
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It is preferable not to use other live respiratory vaccines
within two weeks of live IBV vaccine administration.
Respiratory viruses compete for the same receptor sites on
the upper respiratory mucosa and the antibody response
will be affected.
It may be able to administer a Newcastle Disease vaccine
in combination with an IBV vaccine; this is recommended
in areas with high challenges. The recommendations of the
pharmaceutical companies should always be followed.
Conclusions
The presence of IBV within a flock can have a considerable impact on the economic performance of the current
and subsequent flocks. It is essential that adequate biosecurity (of personnel and equipment) and appropriate
vaccination programs are in place if infection with IBV
is to be avoided. Some key management focus points for
doing this are given below.
Key Management Focus Points
Treatment
In cases of IBV challenge, antibiotics will have no effect
on the IB virus itself. However, as IB virus causes a deficiency in non-specific immunity and increases the risk
of a secondary bacterial infection, mainly E. coli. The
use of a broad spectrum antibiotic for the prevention of a
secondary bacterial infection is appropriate. Use smaller
spectrum antibiotics to treat infections after culture and
sensitivity of the bacteria involved has been established.
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Monitoring
Monitoring of vaccine response should be part of the
vaccine program. Blood for ELISA testing should be
collected on a regular basis to monitor the mean titer
response and the coefficient of variation (CV%). The
mean titer measures the immune response of the flock
giving information about the antibody response of a flock
after vaccination. The CV % gives an indication on variability of the mean titer response of a flock. The lower the
CV%, the more uniform the distribution of the titers and
the better the application of the vaccine. From an application with a live IBV vaccine the CV% should be less than
50%.
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Remember that these titer values may vary according to
type of bird, age, vaccine type and vaccination program
and that every company should establish their own
baselines for mean titer and CV%.
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The use of blue dyes with water vaccination is recommended to monitor vaccine intake after water vaccination
by tongue stain scoring. It also acts to stabilize the water
and will reduce chlorine and sometimes heavy metals.
Auditing of the entire vaccination process should be done
on a regular basis.
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Infectious bronchitis virus (IBV) is caused by a corona
virus that is easily spread within and between flocks.
This virus is very hardy and survives well in the environment.
IBV is not known to be a risk to human health.
IBV affects birds of all ages and incidence occurs
worldwide.
IBV is highly infectious and only a few virus particles
can start an infection.
Transmission is via direct and indirect contact between
poultry and poultry premises. People, vehicles and
equipment can spread the virus.
Placing chicks on farms not cleaned and disinfected
properly or on built up litter increases risk of an IBV
challenge.
Multi-age premises pose a very high risk of transmission and infection of IBV.
The development of a strong immune system in the
young chick is vital to IBV protection. Early bodyweight gains with good uniformity need to be achieved.
Diets must be of good quality and contain the recommended levels of protein and vitamins to ensure proper
development of the immune system.
High biosecurity standards are very important to prevent
immunosuppressive diseases such as Chicken Anemia
Virus (CAV), Infectious Bursal Disease (IBD), Reo
Virus and mycotoxins, which may increase the severity
of IBV infections.
Other respiratory challenges must be properly controlled
as well, such as Turkey Rhinotracheitis (TRT), Avian
Influenza (AI), Newcastle Disease (ND) and Infectious
Laryngotracheitis (ILT).
Many vaccinations are done in the first weeks of life
and must be achieved with minimum stress levels to the
chicks. In the hatchery the route of vaccination is very
important, as is the accuracy of vaccination.
Multiple vaccinations with different strains are needed
for proper protection.
Vaccination must follow standard operating procedures,
which incorporate proper vaccination techniques to
prevent trauma and secondary bacterial infections.
Monitoring the presence of IBV strains in the field
is helpful in determining strains to incorporate into a
vaccination program.
Select vaccine strains that will be most effective against
the field strains present in a region.
0509-AVN-020
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